The BBC Mi­cro was home to dozens of fan­tas­tic coin-op con­ver­sions that be­lied its schol­arly back­ground. Mar­tyn Car­roll speaks to a num­ber of well-known coders to find out why the Beeb was a good fit for faith­ful ar­cade clones


he BBC Mi­cro was al­ways a stu­dious ma­chine. It was ex­pen­sive: the pre­ferred Model B cost as much as £399 in 1982, which was around three times more than com­pet­ing mi­cros, like the Com­modore VIC-20 and Sin­clair Spec­trum. It was ed­u­ca­tional: Acorn de­signed the ma­chine for the BBC’S Com­puter Lit­er­acy Project and off the back of that BBC

Mi­cros in­fil­trated class­rooms up and down schools of the UK. As such, a huge amount of ed­u­ca­tion soft­ware was de­vel­oped for the ma­chine.

The BBC Mi­cro might have been ex­pen­sive and ed­u­ca­tional, but it cer­tainly wasn’t elit­ist.

Many games were avail­able too, of course, and a num­ber of in­flu­en­tial mas­ter­works like Elite,

Ex­ile and The Sen­tinel be­gan life on the sys­tem. Fur­ther­more, the Beeb wasn’t just about weighty ti­tles that cre­ated whole worlds in­side 32K of mem­ory – it was also adept at run­ning pure ar­cade games based on the hit coin-ops of the day. If you wanted to play an au­then­tic game of Space In­vaders, Pac-man, Don­key Kong or Frog­ger at home then you were in luck. In fact, you could ar­gue that no other com­puter could repli­cate the golden age of ar­cades with quite the same verve, as­sur­ance bril­liance as the Beeb.

De­spite its aca­demic lean­ings, the BBC Mi­cro was a good plat­form for ar­cade-style games. Pro­gram­mer Kevin Ed­wards coded the Galax­ian/ Galaga clone Galaforce for Su­pe­rior Soft­ware and he ap­pre­ci­ated the per­for­mance and flex­i­bil­ity that the hard­ware of­fered. “It was equipped with a fast, 2MHZ 6502 CPU which gave the ma­chine a lot of horse­power,” he says. “This was im­por­tant as it didn’t have any hard­ware sprites. In ad­di­tion to this, it had a cus­tom video ULA and 6845 dis­play con­troller that gave the user lots of dif­fer­ent graph­ics modes to choose from. Some were low res­o­lu­tion, with four or 16 colours, and oth­ers were higher res­o­lu­tion, but only sup­ported two colours. All of these modes were bitmapped, rather than char­ac­ter-based, which al­lowed ev­ery screen pixel to be changed in­de­pen­dently with­out lim­i­ta­tion – per­fect for writ­ing 3D wire­frame or shaded games. The 6845 also al­lowed you to do hor­i­zon­tal hard­ware scrolling that was per­fect for port­ing games such as De­fender and Scram­ble.”

Jonathan Grif­fiths con­curs, hav­ing de­vel­oped the faith­ful Scram­ble clone Rocket Raid for Acorn’s soft­ware divi­sion, Acorn­soft. For him the abil­ity to pro­duce pixel-per­fect an­i­ma­tion and smooth scrolling was key. “The dou­ble-buffered RAM meant that the screen ac­cess was in­ter­leaved with the pro­ces­sor ac­cess,” he says, “so the soft­ware could read and write to the screen mem­ory when­ever it wanted with­out hav­ing to worry about screen glitches. And then the 2MHZ 6502 was fast enough to keep up with the screen re­fresh, as long as the soft­ware was writ­ten ef­fi­ciently. One of the things I did in Rocket Raid was set up a timer in the 6522 sup­port chip to tell me the ver­ti­cal po­si­tion of the elec­tron beam used in the TVS and mon­i­tors, so I could en­sure I only re­drew the graph­ics that weren’t too close to the beam and avoided the oc­ca­sional ‘tear­ing’ of sprites. Also, the ULA for colour han­dling and the 6845 for screen res­o­lu­tion and po­si­tion meant that the colours of the ar­cades could be repli­cated, which made things easy.”

Praise for the BBC’S colour pal­ette is some­thing that Matthew Atkin­son echoes. Matthew, who would go on to de­velop the all-time Beeb

It was equipped with a fast, 2MHZ 6502 CPU which gave the ma­chine a lot of horse­power Kevin Ed­wards

clas­sic Rep­ton 3, wrote the of­fi­cial con­ver­sion of Tem­pest for Atarisoft (al­though it was ul­ti­mately pub­lished by Su­pe­rior Soft­ware af­ter Atarisoft abruptly quit the Acorn scene). He says, “Tem­pest is a colour­ful game that looks best with a full eight-colour dis­play, some­thing the BBC was good at. Other com­put­ers used colour screen at­tributes which didn’t work as well. If you look at other 8-bit con­ver­sions – in­clud­ing my own one for the Acorn Elec­tron – they look a bit drab in com­par­i­son. A phrase I came across re­cently is ‘al­ways choose colour over res­o­lu­tion’. Most of the early Atari ar­cade games used a 1MHZ 6502 with var­i­ous hard­ware en­hance­ments to as­sist the dis­play. The BBC had a 2MHZ 6502 which gave you some ex­tra power to try and em­u­late the ar­cade hard­ware.”

Matthew also praises the ma­chine’s sound chip which was ca­pa­ble of em­u­lat­ing the zaps, pings and crashes that ac­com­pa­nied your typ­i­cal ar­cade game. “The sound on the BBC was com­pa­ra­ble to other 8-bit com­put­ers that used more ad­vanced sound chips. The down­side was the amount of pro­cess­ing power used to ser­vice the sound gen­er­a­tion, some­thing that was done more in hard­ware on other ma­chines.”

nother Beeb afi­cionado is pro­gram­mer Peter John­son. He be­gan his ca­reer writ­ing ar­cade clones for the ma­chine, in­clud­ing Q*bert and Death­star (a ver­sion of Sin­istar) for Su­pe­rior Soft­ware, be­fore mov­ing over to other sys­tems. He’s well placed to dis­cuss the BBC Mi­cro hard­ware com­pared to its con­tem­po­raries. “The BBC Mi­cro eclipsed the Spec­trum in terms of tech­ni­cal ca­pa­bil­i­ties,” he states. “The C64 had other ad­van­tages that the Beeb couldn’t match, such as hard­ware sprites and scrolling, al­though the Beeb’s pro­ces­sor was twice as fast to com­pen­sate. An­other dif­fer­ence was a brighter colour pal­ette. To me, many C64 games ap­peared a bit washed out – al­though I would have loved to have had a few more shades to pick from than the eight true colours the Beeb was lim­ited to. Skin tone choices were lim­ited to yel­low, ma­genta, pure black or pure white, for in­stance, so re­al­ism was out of the win­dow. This prob­a­bly in­flu­enced the style of games we saw on that plat­form, as it favoured the ab­stract style.”

Peter also re­calls the nov­elty of mak­ing the Beeb ‘speak’. “Add-ons like the speech sys­tem were fun. Voiced by news­reader Ken­neth Ken­dall, it could

The BBC Mi­cro eclipsed the Spec­trum in terms of tech­ni­cal ca­pa­bil­i­ties Peter John­son

only speak from a lim­ited vo­cab­u­lary. When the boss in Sin­istar had fin­ished build­ing, it would laugh and say ‘I am com­plete!’, so when I cloned it in Death­star I used the chip to make it say, ‘R R R, I an com­plete!’, which was the clos­est I could get. I bet it scared the life out of some­one when they heard it do that for the first time.”

If any­one has any doubts as to how ca­pa­ble the Beeb was at recre­at­ing coin-ops, they only have to look at the early out­put from Acorn­soft. They might have been un­of­fi­cial, but ti­tles like Plan­e­toid (De­fender), Snap­per (Pac-man), Me­te­ors (As­teroids) and Hop­per (Frog­ger) pro­vided

Beeb own­ers with an au­then­tic ar­cade-at-home ex­pe­ri­ence. Qual­ity clones also came from Pro­gram Power (later Mi­cro Power) who scored hits with Killer Go­rilla (Don­key Kong), Mr Ee! (Mr Do!), Frenzy (Qix) and Bum­ble Bee (Lady Bug). And, of course, there was Su­pe­rior Soft­ware which pub­lished a mon­soon of coin-ops clones.

Hav­ing au­thored sev­eral games for Su­pe­rior, Peter han­dled the of­fi­cial Beeb con­ver­sions of Yie-ar Kung Fu, Mikie and Arkanoid for Ocean’s Imag­ine la­bel. “The BBC got such a rep­u­ta­tion due to the amaz­ing early work that Acorn­soft did in repli­cat­ing ar­cade clas­sics of the time, set­ting an ex­am­ple for us all to fol­low,” he con­tin­ues. “I al­ways felt I should be as­pir­ing to match the qual­ity of its early ti­tles with all my con­ver­sions.”

How­ever, not ev­ery­one we spoke to felt that the Beeb was ideally suited for coin-op con­ver­sions. “It was only ever a mid­dling fit for ar­cade clones,” says Nick Pelling, the cel­e­brated au­thor of Ar­ca­di­ans (Galax­ian) and Zalaga (go on, guess). “Even though the graph­ics mem­ory was nicely laid out, the amount of mem­ory left over for squeez­ing code into was never re­ally enough.”

Ah, mem­ory. On 8-bit com­put­ers there was never enough RAM, and the Beeb suf­fered more than most. The Model A had just 16K so it was largely over­looked as a gam­ing plat­form. The Model B had 32K, which was prefer­able but still lim­ited. “Mem­ory was an is­sue, cer­tainly,” ad­mits Jonathan Grif­fiths. “We typ­i­cally wanted a colour­ful screen, so that meant Mode 2, which was 20K of our 32K RAM gone im­me­di­ately. And then the 6502 zero-page and stack was an­other 512 bytes. Fi­nally, the BBC OS claimed a fur­ther 3K, so we were left with only 9.5K to craft our mas­ter­pieces. We had to use var­i­ous tricks to claw back as much as we could. One ex­am­ple was in Ge­off Cram­mond’s rac­ing game Revs where he cun­ningly put bits

We were left with only 9.5K to craft our mas­ter­pieces, and that tiny bud­get in­cluded all our graph­ics Jonathan Grif­fiths

of the soft­ware in the screen dis­play, in the sky area, by set­ting the pal­ette en­tries for ev­ery pixel to be blue. That def­i­nitely shows that we had an is­sue with mem­ory.”

Matthew Atkin­son also strug­gled with the lack of RAM. “The stan­dard ma­chine was lack­ing in mem­ory com­pared to some other com­put­ers,” he says, “but it could be cir­cum­nav­i­gated to some ex­tent by re­pro­gram­ming the 6845 video chip to re­claim more mem­ory in high-res­o­lu­tion colour modes. The BBC could have used an ex­tra 16K in the ‘side­ways’ RAM slot as stan­dard. That would have been so lib­er­at­ing for pro­gram­mers and led to bet­ter games.” The BBC B+ and Mas­ter se­ries mod­els did come with ex­tra RAM, and a num­ber of games would au­to­mat­i­cally de­tect it and de­liver en­hance­ments if present. How­ever, the Model B re­mained the core ma­chine and pub­lish­ers un­der­stand­ably tar­geted that first and fore­most.

While the mem­ory was a hur­dle to over­come, the con­sen­sus from the pro­gram­mers was that the Beeb was a great ma­chine to de­velop games for. Kevin Ed­wards says, “BBC BA­SIC had a built-in as­sem­bler that made it very easy to as­sem­ble and test your own 6502 code. All the top games were writ­ten in ma­chine code and this was so easy to do with a stan­dard Beeb – ideally with a floppy drive. The code as­sem­bled fast and could be tested within sec­onds. There was no need for ex­ter­nal de­vel­op­ment ma­chines or ex­tra hard­ware. It also had a great key­board which was im­por­tant when you spent all day, cod­ing.”

onathan Grif­fiths was also thank­ful for the as­sem­bler that was in­cluded within the ma­chine’s BA­SIC in­ter­preter. “It was a huge ben­e­fit. I taught my­self 6502 as­sem­bler on the BBC’S pre­de­ces­sor, the Acorn Atom. That had the same com­bined BA­SIC and as­sem­bler, but crammed into just 8K rather than the 16K that the BBC had. Thanks to the ex­tra space there was now float­ing-point arith­metic, nicer BA­SIC and an even bet­ter as­sem­bler. Be­cause it was so easy to swap from BA­SIC to as­sem­bler and back, that made writ­ing test frag­ments much eas­ier.”

Matthew Atkin­son is in agree­ment about the as­sem­bler. “It was fab­u­lous for games de­vel­op­ment, pro­vid­ing the abil­ity to mix as­sem­bler and BA­SIC, cre­ate macros and so on. I later did some de­vel­op­ment work on the Am­strad CPC, which was very sim­i­lar in tech­ni­cal ca­pa­bil­i­ties to the BBC, but much more dif­fi­cult to use in this re­spect.”

ne of the thornier as­pects of the era was the sheer num­ber of un­li­censed ar­cade clones. These could be found on most home com­put­ers, but the Beeb in par­tic­u­lar was a hot­bed of brazen clones. Jonathan Grif­fiths re­veals that he and his cod­ing col­leagues, Neil Raine and Tim Dobson, were given free rein by Acorn­soft, so they’d go out and play the lat­est coin-ops and then divvy up be­tween them which ones they’d con­vert. And Jonathan can’t re­mem­ber any sig­nif­i­cant prob­lems aris­ing.

“There were copy­right is­sues with Snap­per,” he says. “I changed the sprites and that fixed that prob­lem. We got away with Rocket Raid, even though it was even more of a copy of Scram­ble than Snap­per was of Pac-man.”

One the­ory as to why so many clones went un­no­ticed on the ma­chine in­volves the BBC con­nec­tion. Did copy­right hold­ers be­lieve that the broad­caster was in­volved and thought twice about send­ing in the lawyers? Peter John­son doesn’t think so. “This was com­mon across all home com­put­ers, so I don’t think it was the BBC name that put them off. I was more likely that the Us-based com­pa­nies didn’t no­tice at first as the BBC Mi­cro wasn’t big in the States. The home com­puter mar­ket started out small, and it was a more naive time gen­er­ally, with the finer points of what was cov­ered by copy­right or trade­mark laws still to be tested in court. My first game Q*bert re­ceived a cease and de­sist let­ter from Got­tlieb af­ter only a week or two on-sale, but that was be­cause we were us­ing the ac­tual name. Sev­eral years of cloned games un­der dif­fer­ent names fol­lowed – al­though how we never at­tracted a writ for us­ing the word ‘Death­star’ I’ll never know.”

Li­cenc­ing is­sues aside, the fact re­mains that the BBC Mi­cro was a fan­tas­tic plat­form for games. An in­ter­est­ing facet of this is that many gamers will have en­joyed these ti­tles de­spite never ac­tu­ally own­ing an Acorn. You see, with BBC Mi­cros present in so many class­rooms, there would al­most cer­tainly be clan­des­tine disks full of ar­cade games float­ing around, for those af­ter­school com­puter clubs where mem­bers wanted to play Killer Go­rilla rather than Granny’s Gar­den. In this re­spect the not-so-stu­dious BBC Mi­cro served an ed­i­fy­ing pur­pose, en­sur­ing that our kids were well versed in dot munch­ing, bar­rel jump­ing, alien de­struc­t­ing and other es­sen­tial life skills.

It was fab­u­lous for games de­vel­op­ment, pro­vid­ing the abil­ity to mix as­sem­bler and BA­SIC Matthew Atkin­son

» LEFT [BBC Mi­cro] Acorn­soft’s Rocket Raid was a very fine ver­sion of Kon­ami’s land­mark scrolling shooter Scram­ble. » ABOVE [BBC Mi­cro] Mon­sters, heav­ily in­spired by Space Panic, was an early hit for Acorn­soft. » [BBC Mi­cro] Matthew Atkin­son’s...

» [BBC Mi­cro] Sim­ple Space In­vaders clones were ten-a-penny on the Beeb. This is In­vaders from IJK soft­ware. » [BBC Mi­cro] Dun­junz was Bug­byte’s Gaunt­let clone, al­though it did split the ac­tion across four screens. » [BBC Mi­cro] Peter John­son worked on...

» Jonathan Grif­fiths, devel­oper of Snap­per and Rocket Raid. » The pro­lific Peter John­son wrote more than a dozen coin-op con­ver­sions for the Beeb.

» [BBC Mi­cro] Be­fore cre­at­ing Rep­ton, Tim Tyler wrote a ver­sion of Moon Pa­trol that was pub­lished by Su­pe­rior as BMX On The Moon! » ABOVE [BBC Mi­cro] Fol­low­ing a com­plaint, Jonathan Grif­fiths was forced to change the sprites in Snap­per, his Pac-man...

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